You're not likely to get much living in them if you only use them for water. If they've got sports drinks in them, then that's lots of food for bacteria. Don't leave them sitting with sports drink or any residue thereof after your ride - rinse them out. A dishwasher will kill anything - as long as the plastic will survive it. The valve can be the trickiest thing to clean properly.

Do you not wash them; how often does she throw out chopping boards? Unless they are all scratched up inside they won't be providing anywhere for bugs to hide from cleaning.

Personally I'd be more worried about BPAs, which I'm not about to start worrying about! I've got, and use, some ridiculously old bottles; it's more likely cow and sheep shit washing off the fields and getting sprayed up by your wheels that'll make you ill than the contents of your own bottles.

I use the sterilising fluid or tablets that all good supermarkets stock for baby bottles. Pop half a tablet in each bottle, another half tablet in an old ice cream tub for the bottle tops, fill them with water, wait half an hour, then rinse out and scrub the mud off the exterior surfaces. Why nobody has launched a "performance" version for cyclists, with the customary 2000% mark-up, I don't know.

I tend to soak mine in very hot water after each ride. Using energy products and not washing them properly could be a bit dodgy. Also as many have mentioned, most can go on the top rack of the dishwasher. That said, if the Mrs is that concerned she won't mind you buying some nice new ones will she!

In days of old, when riders and teams did not seem to have a limitless supply of bottles with which to litter the place, a standard job was getting all bottles, fill a bath in the hotel with hot water, and empty a large amount of Milton or similar into it and submerge the bottles and lids. Leave for 30 minutes, rinse and scrub clean bottles, no problem with bugs.

Every ride my 2 bottles get a wash outside,then once a week they get a Milton tablet each,after a good soaking with a milton tab,they get a good flushing with cold water,and are ready for the next rides.SAFE ENOUGH FOR BABIES,SAFE ENOUGH FOR BIKIES!Wash out thoroughly you wont taste the Milton.New bottles 2 yrs ago still looking ok,3 rides per week.Enjoy,FOXYLOXY